Photo-printing apparatus



Jan. 2,' 1968 'r. P. c. BREUERS Y Y 3,

PHOTO-PRINT ING APPARATUS Filed June 8, 1 965 2 Sheets-Sheet 1 INVENTOR THEO PIERRE CHRET/EN Beau/5 5 ATTORNEY 1968 T. P. c. BREUERS 3,

PHOTO-PRINTING APPARATUS 2 Sheets-Sheet 2 Filed June a, 1965 'INVENTOR 77/50 PIERRE CHRISTIE/Y BREUEKS ATTORNEY United States Patent 3,361,047 PHOT0-PRINTING APPARATUS Theo Pierre Chretien Breuers, Venlo, Netherlands, assignor to Chemische Fabriek L. van der Grinten N.V., Venlo, Netherlands, a corporation of Dutch law Filed June 8, 1965, Ser. No. 462,227 Claims priority, application Netherlands, June 17, 1964, 64-6,895 2 Claims. (Cl. 9577.5)

The invention relates to a photo-copying apparatus comprising a rotating exposure cylinder made of glass or similar material of poor heat-conductivity, a system of narrow belts, arranged side by side with small interspaces, for pressing the printing set (original and light-sensitive material) against the cylinder, and a lamp mounted inside the cylinder for exposing the printing set through the wall of the cylinder.

As a rule, the belts in known apparatus of this type are moving endless belts, which are passed around a part of the cylinder and further around a number of guide rollers and driving rollers respectively. With a View to keeping the belts in alignment, some rollers are provided with thin discs, which protrude between the belts. Thus, the belts are spaced slightly apart, e.g. with slit-shaped interspaces of 1 to 2 mm.

The glass cylinder is heated by the radiation of the lamp. When no copies are made, heat is transmitted from the cylinder to the belts in the places where the belts contact the cylinder. In these places the cylinder is cooled as it were. In the places where there are slits between the belts, the cylinder transmits no heat, or at least much less. Since glass is a poor heat-conductor, there is only a small heat-exchange across the surface of the cylinder. Thus the zones where the slits are present continuously remain warmer than the rest of the surface.

If in this situation a printing set is fed int-o the apparatus, heat is transmitted from the cylinder to the lightsensitive material. In the warmer zones of the cylinder more heat is transmitted than in the cooler zones, and thus the light-sensitive layer of the copying material receives the same pattern of cooler and warmer zones as that present on the cylinder.

Since the chemical reactions which during exposure take place in the light-sensitive layer of the copying material, such as diazotype material, proceed more rapidly as the temperatrue is higher, in the areas of the light-sensitive material which are heated by the warmer zones of the cylinder t-he light-sensitive substance is converted more rapidly during exposure than in the areas whose temperature depends upon the cooler cylinder zones. The fact that the conversion of the light-sensitive substance in the warmer zones is more rapid and consequently more thorough in a given time, as compared with the slower conversion in the cooler zones, which is less thorough in the same time, results in a virtual over-exposure of the warmer zones; in a diazotype copy with an under-exposed background, of the kind frequently made of technical drawings, these differences are visible in the form of narrow streaks, whose background is less under-exposed than their surroundings and which, parallel to each other and spaced at distances corresponding to the width of the belts, extend along the full length of the copy.

The above-mentioned temperature differences existing on the cylinder surface arise when the apparatus is running on no-load, i.e. when no copies are made, although the lamp is burning and cylinder and belts are driven. When after such a no-load period diazotype copies are made with an under-exposed background, it may happen that the streaks on the copies are visible.

When subsequently copies are continuously made, the heat is no longer transmitted directly from the cylinder to fit the belts, but via the printing sets. The temperature differences are then equalized, so that the phenomenon in question is less pronounced, although it may also occur in this situation.

It is the object of the invention to obviate this disadvantage, and for this purpose an apparatus as referred to in the preamble is provided with a number of orifices for the discharge of cooling air, said orifices being provided in a stationary device outside the cylinder and being directed at the slit-shaped zones, which are present between the belts, where the latter are pressing against the cylinder.

Preferably this is realized in such a way that the orifices are simple perforations arranged in rows in the wall of a blowing box, said wall being curved and being substantially uniformly spaced from the moving cylinder surface.

The invention will now be described more fully with reference to the accompanying diagrammatical drawings, in which FIGURE 1 is a diagrammatical vertical cross-section through an apparatus according to the invention;

FIGURE 2 is a perspective view of part of the apparatus according to FIGURE 1;

FIGURE 3 is a perspective view of the part of the apparatus according to FIGS. 1 and 2, which is essential in view of the invention.

A lamp 1, e.g. a high-pressure mercury lamp, is placed in the centre line of a glass cylinder 2, which is adapted to rotate about its own axis. A number of narrow endless conveyor belts 3, arranged side by side, are passed around and a number of guide-rollers 4, 5, 6, 7, and 8, the rollers 4 and 8 being provided with disc-shaped parts 9, each of which protrudes between two belts, by which means the belts are kept in alignment. Narrow interspaces, e.g. with a width of 1-2 mm., are thus formed between the belts 3.

When copies are made, the glass cylinder 2 is rotatably driven, and superimposed originals and sheets of light-sensitive material are guided between the belts 3 and the cylinder 2, and are pressed against the cylinder- 2 by means of the belts 3, so that they are moved at the same rate as said parts 2 and 3, the lamp 1 giving an exposure which is sufiicient for obtaining, after development, a good photo-copy of the original on the light-sensitive material.

In the exposure section a considerable part of the surface of the cylinder 2 is surrounded by a blowing box 10, which is connected by an air-supply pipe 11, in which is fitted a control valve 12, to an air blower 14. As is clear from FIGURES 2 and 3, the box 10 is provided with rows of small perforations 13, through which the air can escape from the box, which for the rest is closed, and these rows of perforations are situated exactly opposite the intersp-aces between the belts 3. In this Way the glass cylinder, which is cooled by means of the belts 3 in those places where they contact the cylinder when no paper is present between the belts and the cylinder, is also cooled between said belts, in consequence of which the surface can be kept at a uniform temperature. By means of the control valve 12 the quantity of air blown out can be regulated in such a way that it produces the same cooling effect as the belts.

On the copies no influence of the slits between the belts will then be visible any longer.

What I claim is:

-1. A photo-printing apparatus comprising a rotating exposure cylinder made of glass or similar material of poor heat-conductivity, a system of narrow belts, arranged side by side with small interspaces, for pressing the original and light-sensitive material against the cylinder, and a lamp mounted inside the cylinder for exposing the original and light-sensitive material through the wall of 3 the cylinder, characterized in that the apparatus is provided with a number of orifices for the discharge of cooling air, said orifices being provided in a stationary device outside the cylinder and being directed at the slitshaped intersp aces which are present between the belts, Where the latter are pressing against the cylinder.

2. An apparatus according to claim 1, characterized in that the orifices are simple perforations arranged in rows in the Wall of a blowing box, said well being curved and being substantially uniformly spaced from the cylinder surface.

4.- References Cited UNITED STATES PATENTS 910,832 1/ 1909 Lukacsevics 95-775 3,060,828 10/1962 Ackerrnann 95-775 FOREIGN PATENTS 522,411 3/1956 Canada. 1,266,482 6/ 1961 France.

10 NORTON ANSHER, Primary Examiner.

M. H. HAYES, Assistant Examiner. 

1. A PHOTO-PRINTING APPARATUS COMPRISING A ROTATING EXPOSURE CYLINDER MADE OF GLASS OR SIMILAR MATERIAL OF POOR HEAT-CONDUCTIVITY, A SYSTEM OF NARROW BELTS, ARRANGED SIDE BY SIDE WITH SMALL INTERSPACES, FOR PRESSING THE ORIGINAL AND LIGHT-SENSITIVE MATERIAL AGAINST THE CYLINDER, AND A LAMP MOUNTED INSIDE THE CYLINDER FOR EXPOSING THE ORIGINAL AND LIGHT-SENSITIVE MATERIAL THROUGH THE WALL OF THE CYLINDER, CHARACTERIZED IN THAT THE APPARATUS IS PRO- 